The present invention relates to a method for fabricating a diffusion barrier metal layer in a semiconductor device capable of preventing the substance of a metal wiring from being diffused into its underlayer during the formation of the metal wiring of the semiconductor device, and more particularly, to a method for fabricating a diffusion barrier metal layer which can be used in a deep and narrow contact.
Generally, a ruthenium oxide layer (RuO.sub.2) is used as a diffusion barrier metal layer in a highly integrated semiconductor device above 256M DRAM, and used as a glue layer of a metal wiring formed of aluminum, tungsten or copper. In prior arts, the ruthenium oxide layer is formed by the physical vapor deposition (PVD) or the chemical vapor deposition (CVD) method. In case of the PVD method, ruthenium and oxygen are compounded to form the ruthenium oxide layer. In case of the CVD method, ruthenium source gas and oxygen are compounded to form the ruthenium oxide layer through the metal organic chemical vapor deposition (MOCVD) method.
However, in case where the ruthenium oxide layer is formed by the CVD method, impurities are introduced into the ruthenium oxide layer. This increases the resistance value of the layer. In case that PVD is used, the step coverage of the ruthenium oxide layer is poor, and a silicide layer may be formed by the reaction of the ruthenium oxide layer and silicon. Furthermore, during the deposition of the ruthenium oxide layer, the oxidation rate is too low to form a stable ruthenium oxide layer.